Thermally actuated circuit delay switch connector



March 3, 1964 M. LEICHSENRING THERMALLY ACTUATED CIRCUIT DELAY SWITCH CONNECTOR 2 Sheets-Sheet 1 Filed May 2, 1962 INVENTOR.

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United States Patent 3,123,686 THERMALLY ACTUATED CIRCUET DELAY SWITCH CUNNECTGR Max Leiehsenring, 4525 N. Francisco St, Chicago, Ill. Filed May 2, 1962, Ser. No. $1,797 8 Claims. (Cl. 260-51) The present invention relates to delayed action power switches which respond to operation of a control to efilect a delayed opening of a power circuit.

A power switch of this character can provide in a number of environments distinct advantages in the control of electric lights, for example. When installed in a bedroom, such a switch can permit a user to move a switch control to an off position and then make his way into bed before the switch operates to turn out the light. When installed to control an outside light for a residence or other building, such a switch permits a person to move a switch control to its oil position before leaving the building and then proceed away from the building before the switch turns out the light. By keeping a controlled light burning for a limited period of time after the switch has been manually operated to turn out the light, such a switch enables the user to avoid the hazard and inconvenience of having to move away from the switch in the dark after the switch control has been operated.

However, prior switches of this character have tended to be impractical because of structural complexity, high manufacturing costs, lack of dependability, bulkiness, and other factors which have detracted from the advantages which may be gained from use of the switches.

Care object of the invention is to provide a new and improved delayed action power switch well adapted for general residential and similar usages, and having an inierent practicality by virtue of being well adapted for economical manufacture and having an inherent capability of operating dependably and efliciontly in service.

Another object is to provide a delayed action power switch as recited in the preceding object which occupies a very small space.

Another object is to provide a novel switch connector plug of small size adapted to be plugged into an ordinary household power outlet socket in the manner of a conventional electrical plug and serving to provide an efficient, dependable delayed action opening of the electrical circuit through the switched connector plug itself.

Another object is to provide a compact switch coupling adapted to couple an ordinary electrical plug to an ordinary electrical socket, and having an extremely economical construction which provides response to operation of a manual control on the coupling to provide an emcient and dependable delayed action opening of the circuit through the coupling in the manner described in relation to the preceding objects.

Another object is to achieve the objects previously recited by means of structure in which the working parts which effect the delayed opening of a circuit are conesscntially to a simple bimetallic element.

Other objects and advantages will become apparent from the following description of the exemplary forms or" the invention illustrated in the drawings, in which:

FIGURE 1 is a perspective view illustrating in a somewhat exploded form the relationship to a plug and a socket of a delayed action switch coupling constructed in accordance with the invention;

FIG. 2 is a horizontal sectional view of the coupling taken generally with reference to the line 2-2 of FIG. 1;

3 is a vertical sectional view taken along the line 33 of 2;

PEG. 4 is a simplified sectional view taken along the irregular line :4 of FIG. 2;

FIG. 5 is an exploded perspective view of the switch 3,123,686 Patented Mar. 3, 1%64 2 operator and internal switching elements used in the cou- F FIG. 6 is a perspective view showing the relationship to a power socket of a switched plug constituting a modified form or" the invention;

FIG. 7 is a sectional view taken along the line 7-7 of FIG. 6;

FIG. 8 is a partially sectioned elevational View of a switched plug forming another modified embodiment of the invention; and

HS. 9 is a sectional view taken along the line 99 of FIG. 8.

Referring to the drawings in greater detail, the plugsocket switch or coupling 1i forming the exemplary embodiment of the invention illustrated in FIGS. 1 to 5 comprises a housing 12 formed basically in two parts, a hollow plastic dome l4 defining a generally circular opening 16 into the dome, and a substantially flat circular floor 18 formed of an insulating material and adapted to fit into and close the opening to into the dome 14.

An electrical socket 2%} adapted to receive a conventional electrical plug 22, FIG. 1, is integrally formed with the dome l4 on one side of the dome and defines two electrical socket openings 2A adapted to receive two parallel prongs 35 of a conventional connector plug 22.

Two socket output conductors 28, 29 disposed within the housing 12 are supported by two pins 3%, 31 anchored to the lioor 18. The output conductors 28, 29 extend from the spaced pins 3t), 31 toward the inner ends of the socket openings 24 and terminate in .two upstanding wipe-r cars 32, 33 positioned in inward alinement with the socket openings 24 to press against the prongs as of a plug 22 inserted in the coupling socket 29, as shown in PEG. 2.

Two L-shaped input conductors 3d, 35 are supported within the housing 12 by the pins 3h, 31, as shown in FIG. 3, and project out through the floor 18 to form two spaced parallel socket prongs, also identified by the numbers 34, 35. The prongs 34, 35 of the coupling 16 are adapted to fit into a conventional wall socket 3 5, FIG. 1, in the same manner as would the conventional plug 22,.

Within the housing 12, the input prong 35 is continuously connected electrically to the socket outlet conductor 29. As shown, adjacent ends of the conductors 35 and 29 are stacked together in electrical contact with each other on the common anchor pin 31 which is suitably insulated from both conductors 2d and 35.

The other prong 34 of the coupling 10 is controllably connected to the other socket output conductor 28 by means of a delayed action switch 33, FIGS. 2 and 4, and also by means of a jumper switch 4b in parallel with the delayed action switch 3%.

The delayed action switch 38 comprises an L-shaped conductor 42 which lies hat on the inner surface of the floor 18 and has one end anchored to the pin 36 and stacked in contact with the inner end or" the prong 34, so that the conductor 42 is continuously connected electrically with the prong 3d. The end of the conductor 42 remote from the pin 34) supports a stationary contact 44 of the switch 38.

The contact 44 is opposed by a movable contact 46 supported by the free end of a bimetallic cantilever 48 V which is supported at its other end around the pin 31 As shown in FIG. 4, the pin 36 is electrically isolated by a cylindrical insulator ill from the conductors anchored by the pin 3h. The supported or anchored end of the cantilever 43 is insulated electrically from the input prong 34 by an insulator washer 52.

The anchored end of the conductor 28 is stacked in contact with the anchored end of the cantilever 48. The

Q2! cantilever 43 itself constitutes a low resistance conductor connecting the contact 46 with the socket conductor 28.

A high temperature thermal insulator 56 is wrapped around a major portion of the cantilever 48 and serves as a core about which is wrapped a high resistance electrical heating wire 58.

One end 60 of the heating wire 58 is continuously connected to the input prong 34, as illustrated in FIG. 4. The other end 62 of the heating wire 58 is connected to the other input prong 35 by means of a normally open control switch 64, as illustrated in FIGS. 2 to 5.

When both the prongs 34, 35 are energized, closure of the control switch 64 produces a low Wattage heating of the wire 58. Heat from the wire 58 penetrates through the thermal insulation 56 to effect heating of the bimetallic cantilever 48 which bends toward the conductor 42, FIG. 4, to engage the switch contact 46 with the switch contact 44. This closes the delayed action switch 33 to connect the socket output conductor 28 with the input prong 34. Since the other socket output conductor 29 is already energized, the delayed action switch 38 when closed serves to fully energize the socket 20 for supplying of power to a plug 22 which may be inserted in the socket 20.

It will be appreciated that there is a lapse of time between closing of the control switch 64 and closing of the delayed action switch 38 in the manner described. Immediate energization of the second socket conductor 28 in response to operation of a manual switch control to be referred to is provided by the previously mentioned jumper switch 40 in parallel with the delayed action switch 38.

Both the jumper switch 46 and the control switch 64 are operated by a common switch operator which, in the construction illustrated, comprises a knurled control knob 66 secured to the outer end of a shaft 68 journalled in a boss 79 on the dome 14 of the housing 12. The inner end of the shaft 63 carries a double lobed non-conducting cam 72 designed to operate both the jumper and control switches 49, 64 simultaneously.

In the preferred construction illustrated, the jumper switch 40 comprises two flexible conductors 74, 76 projecting within the dome 14 away from the floor .118 in normally spaced relation to each other and including two normally spaced opposed contacts 78, 80. The conductor 74 is anchored by the pin 35 in tightly engaged relation to the socket output conductor 23. The conductor 76 is supported by and in electrical contact with the input prong 34. The control switch 64 is also formed by two conductors 82, 84 which project within the dome 14 away from the floor 18 in generally parallel normally spaced relation to each other and which include two normally spaced opposed contacts 86, 83. The conductor 32 is anchored to the floor 18 by an insulated rivet 9t) and is connected to the end 62 of the heating wire 58, The conductor 84 is anchored by the pin 31 in engaged electrical contact with the socket conductor 29.

The double lobed non-conducting control cam 72 is disposed between the two conductors 76, 82 of the switches 4t), 64, whereupon rotation of the control knob 66 to the on position causes the cam 72 to move the conductor 76 toward the conductor 74 to close the switch 40 and to move the conductor 82 toward the conductor 34 to close the switch 64.

Assuming that the coupling 10 is plugged into a socket 36 and that a light 2, FIG. 1, is connected by a plug 22 with the socket 20, rotation of the control knob 66 to its on position effects an immediate energization of the light 92 through an immediate closure of the jumper switch 40. Closure of the control switch 64 simultaneously with the jumper switch 40 starts heating of the wire 58 and eifects a somewhat delayed closing of the delayed action switch 38 while the light 92 continues to burn.

Rotation of the control 66 to its oi position opens both the jumper switch 40 and the control switch 64. This interrupts the current flow through the high resistance low wattage heater wire 58. However, the bimetallic cantilever 48 does not cool immediately and holds the contact 46 in engagement with the contact 44 to continue energization of the light 92 through the delayed action switch 33. Moreover, the time required for the bimetallic element 48 to cool and open the switch 38 to turn out the light 92 is extended by the thermal insulation provided by the insulator 56 covering that portion of the cantilever most directly heated by the wire 58. However, the cantilever 48 does cool and opens the delayed action switch 38 after a period of time which can be predetermined to have the desired reasonable value. It will be appreciated that the time required for the switch 38 to open after the control 66 has been operated can be changed by varying the amount of insulation 56 provided for the cantilever and through other changes in dimensions, etc., which can affect the thermal value and physical responsiveness of the parts. The bimetallic cantilever 48, which moves the contact 46 into and out of engagement with the contact 44, can be accurately described as a thermal actuator for the movable contact 46. The inbuilt physical character of the cantilever 48 which causes the free end of the cantilever supporting the contact 46 to move downwardly with reference to FIG. 4, upon heating of the cantilever and which causes the free end of the cantilever to move upwardly upon cooling of the cantilever can be accurately described as the thermal polarity of the cantilever or actuator 48.

The physical relationship of the parts and the thermal polarity of the thermal actuator 43 are such that the actuator upon being heated engages or closes the contacts 44, 46 and upon cooling, opens the contacts 44, 46.

In the modified construction illustrated in FIGS. 6 and 7, component elements similar to those in the construction just described are identified with the same reference numbers with the addition of the suflix a.

The switching plug 10a of FIGS. 6 and 7 is simplified in relation to the coupling 16 previously described by elimination of the socket 29 of the coupling 10, FIG. 1, and replacement of this socket with two outlet wires 96, 9%, FIG. 7, which together form an electrical outlet cord 160. The construction of the dome 14a is simplified by formation oi a simple cord opening H92 in place of a plug socket. The wire 5 6 is connected to the output conductor 74a of the jumper switch 4th and the output conductor wire 98 is connected to the energized input conductor 84a of the control switch 64a.

In another modified embodiment shown in FIGS. 8 and 9, component elements similar to those of the embodiment illustrated in FIGS. 6 and 7 are identified with the same reference numbers with the use of the suffix b.

In this form, the cam 72b operated by the knob 66b to control the switches 40b and 64b is modified to be only a single lobed cam, rather than a double lobed cam, so that the cam 72]) operates to close the switches 49b and 64b one at a time rather than simultaneously.

This gives the user the option of closing only the jumper switch 4% which serves to immediately energize the output cord liltlb and to subsequently deenergize the output cord 1%!) immediately upon turning of the control 6617 to its off position. In the alternative, the user can turn the control 66b to close only the control switch 64!). This produces a delayed energization of the cord 100i; and subsequently effects a delayed deenergization of the cord 10% upon turning of the control 66b to its off position. Thus, this embodiment provides the user with the option of determining whether or not there will be a delay in the deenergization of the main circuit when the control is turned to its off position.

The invention is claimed as follows:

1. A delayed action plug-socket switch comprising, in combination, a housing including a generally hollow dome defining an opening thereinto and a floor interfitting with said dome to close said opening thereinto, both said dome and said floor being formed of insulating materials, said dome including a socket integrally formed on one side of said dome and defining two prong receivoneness ing openings, first and second socket outlet conductors mounted in said housing in inward aligned relation to said respective prong receiving openings, first and second electrical plug prongs supported on said floor and projecting therefrom away from said dome, means in said housing connecting said first prong to said first socket conductor, first and second delayed action switch contacts disposed within said housing, a thermal actuator disposed within said housing and being connected to said second contact to move said second contact into and out of engagement with said first contact upon heating and cooling of the actuator, one of said contacts being connected electrically to said second prong and the other of said contacts being connected electrically to said second socket conductor, a thermal insulator disposed within said housing in closely adjacent thermally insulating relation to said actuator to delay cooling of the actuator, an electrical heater disposed within said housing in proximate heat transferring relation to said actuator and having two energizing terminals one of which is connected to one of said prongs, a normally open control switch disposed within said housing and connecting the other one of said heater terminals to the other one of said prongs, a normally open jumper switch disposed within said housing and connecting said second prong and said second socket conductor, and manual operating means extending from outside said housing into the housing and operatively coacting with said control switch and said jumper switch within the housing to effect manual opening and closing of said control switch and said jumper switch.

2. A delayed action plug-socket switch comprising, in combination, a housing including a generally hollow dome defining an opening thereinto and a door interfitting with said dome to close said opening thereinto, both said dome and said floor being formed of insulating materials, said dome including a socket integrally formed on one side of said dome and defining two prong receiving openings, first and second socket outlet conductors mounted in said housing in inward aligned relation to said respective socket openings, first and second electrical plug prongs supported on said door and projecting therefrom away from said dome, means in said housing connecting said first prong to said first socket conductor, first and second delayed action switch contacts disposed within said housing, a bimetallic cantilever in said housing supporting said second contact and being positioned to engage said second contact with said first contact upon heating of the cantilever and to disengage said second contact from said first contact upon cooling of the cantilever, one of said contacts being connected electrically to said second prong and the other of said contacts being connected electrically to said second socket conductor, a thermal insulator wrapped around said cantilever in thermally insulating relation thereto, a high resistance resistor wire wrapped around said thermal insulator to heat said cantilever, one end of said resistor wire being connected to one of said prongs, a normally open control switch connecting the other end of said resistor wire to the other of said prongs, said control switch comprising two normaily spaced conductors projecting from said floor with in said dome and including two normally spaced contacts, a normally open jumper switch connecting said second prong and said second socket conductor and comprising two normally spaced conductors projecting from said fioor within said said dome and including two normally spaced contacts, and a switch operator movably supported on said housing for eiiecting relative movement toward and away from each other of the two conductors of each of said control and jumper switches.

3. A manually controlled switch for effecting a delayed cutting oif of electrical power, comprising, in combination, first and second input conductors, a first output conductor connected to said first input conductor, a second output conductor, first and second delayed action switch contacts,

thermal actuating means connected to said second contact to move said second contact into and out of engagement with said first contact, said thermal actuating means being responsive to heating and cooling of the thermal actuating means to move in opposite directions having a predetermined thermal polarity, said thermal actuating means being physically positioned in relation to said first and second contacts and in relation to said thermal polarity of the actuating means to move said second contact into engagement with said first contact upon heating of the actuating means and to move said second contact out of engagement with said first contact upon cooling of the actuating means, one of said contacts being connected to said second input conductor and the other of said contacts being connected to said second output conductor, said thermal actuating means including electrical heating means therefor, a manual control switch; means connecting said manual control switch and said electrical heating means in series between said first and second input conductors to effect, when said manual control switch is closed, energization of said heating means and heating of said thermal actuating means which moves said second contact into engagement with said first contact thereby connecting said second output conductor with said second input conductor and to effect, in response to opening of said manual control switch, deenergization of said heating means causing said thermal actuating means to cool and subsequently move said second contact out of engagement with said first contact thereby disconnecting said second output conductor from said second input conductor; a manually actuated jumper switch connected between said second input conductor and said second output conductor to effect energizetion of the latter independently of said contacts, and a common manual actuator connected to operate both said control and jumper switches.

4. A delayed action plug-socket switch comprising, in combination, a housing including means forming a socket defining two prong receiving openings, first and second socket conductors supported within said housing in inward alignment with said respective openings, first and second electrical plug prongs supported on said housing and projecting therefrom in generally parallel spaced relation to each other, means within said housing connecting said first prong electrically with said first socket conductor, first and second delayed action switch contacts disposed within said housing, thermal actuating means disposed within said housing and being connected to said second contact to move said second contact into and out of engagement with said first contact, said thermal actuating means being responsive to heating and cooling of the thermal actuating means to move in opposite directions having a predetermined thermal polarity, said thermal actuating means oeing physically positioned in relation to said first and second contacts and in relation to said thermal polarity of the actuating means to move said second contact into engagement with said first contact upon heating of the actuating means and to move said second contact out of engagement with said first contact upon cooling of the actuating means, electrical heating means disposed in said housing in proximate heat transferring relation to said thermal actuating means to heat the latter, one of said contacts being connected to the said second prong and the other of said contacts being connected to said second socket conductor, a manual control switch disposed within said housing, a manual actuator extending from outside said housing into the housing and coacting with said control switch to operate the latter; and means connecting said manual control switch and said electrical heating means in series between said first and second plug prongs to effect, when said manual control switch is closed, energization of said heating means and heating of said thermal actuating means which moves said second contact into engagement with said first contact thereby connecting said second socket conductor with said second plug prong and to effect, in response to opening of said manual control switch, deenergization of said heating means enabling said thermal actuating means to cool and subsequently move said second contact out of engagement with said first contact thereby disconnecting said second socket conductor from said second plug prong.

5. A delayed action plug-socket switch comprising, in combination, a housing including means forming a socket defining two prong receiving openings, first and second socket conductors supported within said housing in inward alignment with said respective openings, first and second eloctrically conducting plug prongs supported on said housing and projecting therefrom in generally parallel spaced relation to each other, means within said housing connecting said first prong electrically with said first socket conductor, first and second delayed action switch contacts disposed within said housing, a bimetallic cantilever supporting said second contact and being constructed and positioned to engage said second contact with said first contact upon heating of said cantilever and to disengage said second contact from said first contact upon cooling of said cantilever, one of said contacts being connected electrically to said second prong and the other of said contacts being connected electrically to said second socket conductor, a high resistance resistor disposed within said housing in heat transferring relation to said bimetallic cantilever, said resistor being connected at one electrical end thereof to one of said prongs, a normally open control switch connecting the other electrical end of said resistor to the other of said prongs, said control switch comprising first and second conductors cantilevering in spaced generally parallel relation to each other and including opposed coacting control switch contacts normally spaced from each other, a thermal insulator disposed in thermally insulating relation to a portion of said cantilever which is heated by said resistor, a jumper switch contained within said housing and comprising third and fourth conductors connected respectively to said second prong and said second socket conductor, said third and fourth conductors cantilevering in generally parallel relation to said first and second conductors and in generally parallel normally spaced relation to each other, said third and fourth conductors including opposed coacting jumper switch contacts normally spaced from each other, a rotary switch operator journalled in said housing and including a manual operating grip outside of said housing for rotating the operator, and a double lobed cam connected with said operator for rotation thereby and disposed within said housing between the cantilevering conductors of said control switch and the cantilevering conductors of the jumper switch to close and open said control and jumper switches in unison by effecting movement toward each other of the two cantilevering conductors of each of said control and jumper switches and by eifecting movement away from each other of the two cantilevering conductors of each of said control and jumper switches.

6. A delayed action plug-socket switch comprising, in combination, a housing including means forming a socket defining two prong receiving openings, first and second socket conductors supported Within said housing in inward alignment with said respective openings, first and second electrical plug prongs supported on said housing and projecting therefrom in generally parallel spaced relation to each other, means within said housing connecting said first prong electrically with said first socket conductor, first and second delayed action switch contacts disposed within said housing, a bimetallic cantilever disposed within said housing and movably supporting said second contact, said bimetallic cantilever being thermally polarized and positioned to move said second contact into engagement with said first contact upon heating of said cantilever and to move said second contact out of engagement with said first contact upon cooling of said cantilever, one of said contacts being connected electrically to said second prong and the other of said contacts being connected electrically to said second socket conductor, a resistor disposed within said housing in proximate heat transferring relation to said bimetallic cantilever, said resistor being connected at one electrical end thereof to one of said prongs, a normally o en control switch connecting the other electrical end of said resistor to the other of said prongs and being disposed within said housing, a thermal insulator disposed within said housing and being located in closely adjacent thermally insulating relation to a portion of said cantilever which is heated by said resistor to delay cooling of said cantilever, a normally open jumper switch contained with in said housing and being connected between said second prong and said second socket conductor, and a movable switch operator extending from outside said housing into said housing and operatively coacting with said control switch and said jumper switch to effect manual opening and closing of the control and jumper switches.

7. A delayed action switch comprising, in combination, a first input conductor, a first output conductor, a first switch contact connected to one of said conductors, a second switch contact connected to the other of said conductors, thermal actuating means connecting to said second contact to move said second contact into and out of engagement with said first contact, said thermal actuating means being responsive to heating and cooling of the thermal actuating means to move in opposite directions having a predetermined thermal polarity, said thermal actuating means being physically positioned in relation to said first and second contacts and in relation to said thermal polarity of the actuating means to move said second contact into engagement with said first contact upon heating of the actuating means and to move said second contact outrof engagement with said first contact upon cooling of the actuating means, electrical heating means disposed in proximate heat transferring relation to said thermal actuating means to heat the latter, a second input conductor, a second output conductor connected to said second input conductor, a manual control switch; and means connecting said manual control switch and said electrical heating means in series between said first and second input conductors to effect, when said manual control switch is closed, energization of said heating means and heating of said thermal actuating means which moves said second contact into engagement with said first contact thereby connecting said first output conductor with said first input conductor and to eiiect, in response to opening of said manual control switch, deenergization of said heating means causing said thermal actuating means to cool and subsequently move said second contact out of engagement with said first contact thereby disconnecting said first output conductor from said first input conductor.

8. A delayed action switch comprising, in combination, a housing, first and second output conductors supported within said housing, first and second electrically conducting plug prongs supported on said housing and projecting therefrom in generally parallel spaced relation to each other, means within said housing connecting said first prong electrically with said first output conductor, first and second delayed action switch contacts disposed within said housing, thermal actuating means disposed within said housing and coacting with said second contact to move said second contact into engagement with said first contact upon heating of said actuating means and to move said second contact out of engagement with said first contact upon cooling of said actuating means, one of said contacts being connected electrically to said second prong and the other of said contacts being connected electrically to said second output conductor, said thermal actuating means including electrical heating means having two energizing terminals one of which is connected to one of said prongs, a normally open control switch contained within said housing and comprising first and second conductors cantilevering in spaced opposed relation to each other and being connected respectively with the prong other than said one prong and with the heating means terminal other than said one terminal, a normally open ju'rnper switch eneaese 9 contained within said housing and comprising third and fourth conductors connected respectively to said second prong and said second output conductor and cantilevering in spaced opposed relation to each other, a single switch operator movably disnosed in said housing in operatively coacting relation to said first and second conductors of said control switch and in opetatively coacting relation to said third and fourth conductors of said jumper switch, and a manual switch actuator extending from outside said housing into said housing and coacting with said switch operator for manually actuating said operator to close and open said control switch by eilecting relative movement of said first and second switch conductors thereof toward and away from each other and to effect closing and openl6 ing of said jumper switch by moving said third and control switch and said jumper switch to close and open each switch by electrically connecting and disconnecting said conductors thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

7. A DELAYED ACTION SWITCH COMPRISING, IN COMBINATION, A FIRST INPUT CONDUCTOR, A FIRST OUTPUT CONDUCTOR, A FIRST SWITCH CONTACT CONNECTED TO ONE OF SAID CONDUCTORS, A SECOND SWITCH CONTACT CONNECTED TO THE OTHER OF SAID CONDUCTORS, THERMAL ACTUATING MEANS CONNECTING TO SAID SECOND CONTACT TO MOVE SAID SECOND CONTACT INTO AND OUT OF ENGAGEMENT WITH SAID FIRST CONTACT, SAID THERMAL ACTUATING MEANS BEING RESPONSIVE TO HEATING AND COOLING OF THE THERMAL ACTUATING MEANS TO MOVE IN OPPOSITE DIRECTIONS HAVING A PREDETERMINED THERMAL POLARITY, SAID THERMAL ACTUATING MEANS BEING PHYSICALLY POSITIONED IN RELATION TO SAID FIRST AND SECOND CONTACTS AND IN RELATION TO SAID THERMAL POLARITY OF THE ACTUATING MEANS TO MOVE SAID SECOND CONTACT INTO ENGAGEMENT WITH SAID FIRST CONTACT UPON HEATING OF THE ACTUATING MEANS AND TO MOVE SAID SECOND CONTACT OUT OF ENGAGEMENT WITH SAID FIRST CONTACT UPON COOLING OF THE ACTUATING MEANS, ELECTRICAL HEATING MEANS DISPOSED IN PROXIMATE HEAT TRANSFERRING RELATION TO SAID THERMAL ACTUATING MEANS TO HEAT THE LATTER, A SECOND INPUT CONDUCTOR, A SECOND OUTPUT CONDUCTOR CONNECTED TO SAID SECOND INPUT CONDUCTOR, A MANUAL CONTROL SWITCH; AND MEANS CONNECTING SAID MANUAL CONTROL SWITCH AND SAID ELECTRICAL HEATING MEANS IN SERIES BETWEEN SAID FIRST 